Le nombre de modules du germe de courbe planex a +y b =0

Sans résumé     

Ionic oxygen species formed in the presence of lithium, potassium and cesium

Various thick oxidized Li, K and Cs layers have been analysed. The O²⁻, O₂²⁻ and O₂⁻ ions have been characterized through the multiplet structures of their valence-band spectra. Furthermore, the energy separations between the O 1s core levels and the O 2p valence levels were seen to take some given values for each oxygen species. This provides a new way to unambiguously identify these species. In addition, the above energy separations compare rather well to the free ion values, thus allowing discussion on the representation of the oxygen ions which are formed in the presence of alkali metals in terms of a point-charge model.     

Direct access to 2-debenzoyl taxoids by electrochemistry, synthesis of 2-modified docetaxel analogs

A new route to semisynthetic 2-modified docetaxel analogs is described using electrochemical cleavage of the 2-benzoate as the key reaction. Subsequent reacylation at C-2 followed by sequential deprotections afforded the title analogs. Biological results of selected 2-docetaxel analogs are presented.     

Kinetic-spectrophotometric determination of traces of vanadium(V) by its catalytic effect on the oxidation of 1,4-dihydroxyphthalimide dioxime with bromate

A kinetic-spectrophotometric method for the determination of trace amounts of vanadium(V) is described. It is based on the catalytic action of this ion on the oxidation of 1,4-dihydroxyphthalimide dioxime by bromate, which yields a red-violet product in acidic medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 500 nm and 30°C. Using several kinetic methods (tangent, fixed-time and fixed-absorbance), vanadium(V) in the range 10–400 ng ml^?1 can be determined. The proposed methods are hardly subject to interferences. The tangent method was used for the determination of vanadium in atmospheric particulate matter, human serum and synthetic mixtures. The kinetic parameters of the catalysed and uncatalysed reactions are reported.